The invention relates to a filler neck for a fuel tank having a vent device, particularly for motor vehicles, for receiving fuel from a dispensing pistol and for depositing the fuel into a fuel tank.
Such a fuel filler neck and vent device has been contemplated in German Unexamined Published Patent application (DE-OS) No. 29 52 175 corresponding to U.S. Pat. No. 4,450,880 issued May 29, 1984. This device serves, with a vent device of a constant hollow cross-section, to allow the escape of air displaced from the fuel tank through the vent device into the filler neck and into the outside environment. The vent device extends approximately in parallel to and at a small distance from the filler neck located below the vent device. The filler neck has a larger inside diameter than the outside diameter of the dispensing pistol at an area below the dispensing pistol support. The insertion of the dispensing pistol into the filler neck provides for only a relatively small discharge gap for the escaping air at an area below the dispensing pistol support and at the area of an adjacently arranged fitting piece. During the refueling process, the air located in the tank and displaced by the fuel volume flows through the vent device and possibly through the filler neck in the direction of the dispensing pistol support resulting in the disadvantage that a back pressure is created at the area where the vent device enters the filler neck and producing the undesirable effect of a turning off of the dispensing pistol and the undesirable effect of fuel spilling from the filler neck into the outside environment. Furthermore, because the location of the connection of the end of the vent device to the side of the fuel tank determines the maximum filling level of the fuel tank, this arrangement provides that a relatively large tank volume located above the maximum filling level remains unutilized.
An objective of the invention is to provide a filler neck of the above mentioned type with constructively simple means with the fuel tank volume being optimally utilized and also so that an operationally adequate venting occurs during uninterrupted refueling.
This objective is achieved according to preferred embodiments of the invention by providing a filler neck apparatus which includes a filler neck means having a discharge gap means for the venting of discharged air out of the filler neck means, a means for connecting the filler neck means to the fuel tank, a vent device means having a cross-sectional enlargement forming an expansion space, a means for connecting the vent device means to the fuel tank, and a connecting duct means linking the vent device means to the filler neck means.
When the expansion space is arranged at the vent device and opens through a connecting duct into the filler neck, below which connecting duct the filler neck has a Venturi-type contraction, there is permitted a perfect venting during refueling with no undesirable turning off of the dispensing pistol prior to completion of the refueling process and with no discharge of fuel out of the filler neck into the outside environment. Because the expansion space extends along the vertical axis of the vent device and opens into the filler neck through the connecting duct, the air displaced by the fuel volume in the fuel tank upon refueling proceeds unimpaired through the vent device into the filler neck and is discharged into the outside environment while any fuel particles taken along with the air displaced from the fuel tank experience a reduction in speed in the area of the expansion space resulting in a precipitation of the fuel particles downward into the bottom section of the expansion space and the fuel particles are returned to the fuel tank through the connecting duct and through the filler neck, being supported in this return by the suction effect caused by the Venturi-type contraction formed in the filler neck.
In an especially preferred embodiment of the invention the filler neck, the vent device, and the expansion area are formed in a one-piece development by a blowing process.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment/several embodiments in accordance with the present invention.